The Bitcoin ASIC business is currently away too risky for bigger venture capitalists. And the other problem is that those guys probably would not be happy with some ASIC miners. I guess, in case they would invest, they want at least 51% of your company.
$3.5mill is what KNCminer said they needed for the wafer run, that's petty cash for a venture capitalist, in a sellers market too, would have been even easier. The problem is that engineers and technical people have little idea how to raise funds for a new venture, so they resort to the pre-order path and put up with truckloads of impatient buyers as a result.